Thirty years since the first cases of AIDS were described, there is much to celebrate regarding progress in the treatment and prevention of the disease. Within the past year alone, several studies have revealed that antiretroviral drugs can prevent the sexual transmission of HIV. Yet worldwide, many people who are potentially exposed to the virus avoid finding out whether they carry it, or deny that they are at risk of contracting it. Unless people establish whether they are infected, they will not be able to be adopt the most appropriate preventive measures. As scientists and clinicians, our ability to overcome this denialism will determine whether we ultimately succeed in using combinations of all the preventive and therapeutic tools now available to slow, and eventually stop, the HIV/AIDS pandemic.